Self-adjusting scissors



J.P.mcHARDsoN L94Z308 SELF ADJUSTING SCISSORS Filed Oct. l2, 1932 J. @M/MM NM/@MW A TTORN E Y Patented Feb. i3, i934 D STES Pili* E? FiiQE In this invention there is provided an improvement in scissors, shears or like instruments by which compensation is effected for the loss in tension normally resulting as the point of shearing or intersection of the cutting blades moves away from the pivot. It is a well recognized fact that scissors are less effective at the ends or points of the blades than near the pivot point. This is due I to the loss in leverage and also to the fact that the J- blades may spring apart enough to permit them to slide over the material without cutting it.

Where sheer fabrics, surgical gauze, or other materials, are being cut this difficulty is frequently met with and causes great inconvenience. I

have devised an improvement in such cutting implements so that there is a self-adjustment in tenslon which compensatesior these tendencies and insures full eiciency over the entire range of the cutting blade.

One of the objects of my invention is, therefore, to provide means by which the tension between the blades is increased as the blades approach coincidence, that is, as the point of shear- Y ing moves away from the pivot.

I accomplish this result by a novel arrangement of the pivot pin so that it is controlled by one cutting member and in turn controls the tension relation between the two blades.

A further object of my invention is to provide I an adjustment in tension which may be varied by small increments.

One of the objects of my invention is also to provide an adjustment which is applied automatically in case the scissors are put in opera- 4tion without the adjustment first having been effected by the operator.

The complete advantage and utility oi my invention will be more evident ir'crn the following description of the preferred form as illustrated in the accompanying drawing in which:

Fig. 1 is a side View of the pair of scissors;

Fig. 2 is a longitudinal cross-section oi the closed scissors taken on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged transverse section on the i'. line 3 3 of Fig. 2;

6 one end 7 of which is the customary blade attached to the opposite handle portion 8. The

point of juncture between the parts 7 and 8 car-- ries a shoulderor abutment 9.

The second or complementary blademember 101 also comprises the blade proper 11 and a handle:

portion 12. The two blade members 6 and 10 aref pivoted together by means of a pivot pin 13.

This pivot pin 13 has a right hand screw-threadv 14 at one end which is adapted to pass through` the blade member 6 as indicated in Figs. 2 and 3.

For the purposesoi accomplishing the effect 'de--v sired the pin 13 must be free to rotate inthe member 6 during the use of the instrument and without binding.

The head 15 of the pin 13 is enlarged and may have a keri 16 by which the preliminary adjust-v ment of the scissors is accomplished. The head 15 is notched or toothed around'its periphery as` shown at 17 yto carry out the compensation called. for in the tension o1" the'instrument.

The blade member 10 has a longitudinal groove, channel or recess i8 which extends from the blade portion 11 backwardly toward the handle portion 12. This groove or recessed portion 18 forms a seat against which the head 15 of the pivot pin rests. In this way the blade member 10 is held down toward the member 6 as shown in Figs. 2 and 3.

The groove 18 also forms a longitudinal slide or guideway for an adjustment bar 19. This bar is slotted longitudinally as shown at 20 in Fig. 5. At one end the bar 19 has a tooth 21. At the opposite end the bar has a diagonal shoulder 22.

The bar 19 is held within the recess or groove 18 by means of a set-screw 23 which is screwthreaded into the member 10 as indicated in Fig. 4.

The bar 19 is of sufficient length so that when it is retracted toward the handle 12 the shoulder 22 projects beyond the side of the blade member 10 in the manner shown by dotted lines in Fig. 1. In this position the tooth 21 does not engage the pivot pin 13.

Ii, however, the locking bar is advanced toward the blade portion 11 the shoulder 22 is brought entirely within the corresponding side of the member 10. In this advanced position the tooth 21 engages within one of the spaces between the teeth 17 on the pivot pin.

The above described arrangement of blade members and pivot pin permits preliminary or rough adjustment in tension by screwing the pivot pin 13 down and thus bringing blade member 10 into a shearing position with the opposite blade member.

This relation of parts, however, fails to maintain the desired or uniform tension over the full length of the blades l and l1. With the pin 13 adjusted as above described the tooth 21 is l5 brought up into engagement with the toothed head 15 and the bar locked in position by means of the set-screw 23. In this way the movement of the two blades into coincidence with the resulting change in position of the point of shearing cutwardly of the ends of the blades causes a relative rotation between the pin 13 and the member 6. As the member 10 rotates to the left in Fig. 1 to approach the member 6, pin 13 advances and draws the member l0 with its blade l1 into closed contact with the corresponding member 6 and blade 7. In this manner the tension between the shearing edges is increased as the cutting stroke is completed and this compensates for the loss in leverage at the point of shearing.

If the operator should neglect to seat the locking bar 19 forward the mere act of bringing the shears together will cause shoulder 22 to strike the abutment 9 and this will throw the tooth 2l into engagement with the toothed head 15 so that the resulting friction will maintain the desired tension during subsequent cutting operations.

The above description represents the preferred form of the device. However, it is merely for purposes of example and many changes in minor details will occur to those skilled in the art as being within the scope of the following claims.

What I claim is:-

1. Scissors or the like having a pair of intersecting blade members, a pivot pin loosely screwthreaded in one of said members, an enlarged peripherally toothed head on the end of the pin remote from said member, the second blade member loosely surrounding the pin between its head and the iirst blade member, said pin being rotatably adjustable relative to said surrounding blade member, said blade member having a recessed portion, a lock bar releasably held in said recessed portion of the second blade member and engaging the head of the pin to cause the latter to draw the members together as the blades are moved into coincidence.

2. Scissors or the like having a pair of intersecting blade members, a pivot pin loosely screwthreaded in one of said members, an enlarged toothed head on the end of the pin remote from said members, the second blade member loosely surrounding the pin between its head and the rst blade member, and having a recessed portion, a lock bar, a set-screw holding the bar in the recess, and a tooth on the bar engaging the head of the pivot pin.

3. Scissors or the like having a pair of intersecting blade members, a pivot pin loosely screwthreaded in one of said members, an enlarged, toothed head on the end of the pivot pin remote from said member, a second blade member loosely surrounding the pin and having a longitudinal groove to receive the head of said pin, a lock bar slidable in said grove, a tooth on the bar for engagement with the head of the pivot pin and a set-screw for holding the locking bar against the second blade member.

4. Scissors or the like having a paii` of intersecting blade members, a pivot pin loosely screwthreaded in one of said members, an enlarged toothed head on the end of the pivot pin remote from the said member, a second blade member loosely surrounding the pin and having a longitudinal groove to receive the head of said pin, a set-screw in said groove, a slotted lock bar slidable on said set-screw and engaging the head of the pin at its forward position and contacted when in its rearward position by the first blade member.

JOSEPH PAUL RICHARDSON. 

